The Extraction Research Of Lithiun-ion Battery Characteristic Parameters For Electric Vehicle

The rapid development of electric vehicle industry alleviatesd the pressure of environmental pollution and energy effectively, but at the same time,it produces a series of social problems.The most important problem is that the outlet of the lithium ion is retired from the electric car after using for a long time,the second use of the lithium ion is the best way to reduce the cost of whole life cycle of the battery and enhance the value of retired battery. The key technology of the second use is the extraction method of the retired battery’s health characteristic parameter and the group clustering method. The research of this article is the parameters extraction method of lithium ion in the process of aging, providing the basis for the second use and group clustering method.The battery’s terminal voltage of the constant current charge and discharge is made of the open circuit potential and the potential composition, on the assumption of that under the premise of constant electric potential, get ting the relationship between the terminal voltage and the open circuit potential of the positive and negative electrode. On this basis, using the nonlinear least squares method to extract the battery characteristic parameters and design experiment to validate the method. Under the dynamic condition, using the extended Kalman filtering recursive calculates the approximate value of the battery’s open circuit voltage,then using the equivalent circuit model and nonlinear least square method to realize extracting feature parameters of the anode and design experiment to validate the method.On this basis, extracting feature parameters under different working conditions and getting the trends of characteristic parameters in the process of aging and analysising the performance feature of the characteristic parameters in the process of aging with different temperature, charge and discharge rate. The mechanism of degradation of battery material and the state of degradation can be obtained and as a theoretical basis for the second use of the power battery.Based on the above research, using different dynamic experiments to find the reliable change interval of SOC in order to obtain the total capacity of the battery on the dynamic condition. Then obtain the voltage interval which can be extracted characteristic parameters as the basis of extracting characteristic parameters in the battery pack. Doing different experiment with series battery pack and extracting the characteristic parameters, then analysising the influence of different charging mode. Finally, Using the data of Harbin buses to validate this method. It can be seen from the results of the validation, this method has better estimation precision.